Page:Encyclopædia Britannica, Ninth Edition, v. 16.djvu/190

Rh 180 METEOROLOGY [TERRESTRIAL MAGNETISM. Broun, Charles and Frederick Chambers, Eliot, and Hill, and the following conclusion is the result of their labours. We may assume that the Indo-Malayan region has for the mean of the year a barometric pressure probably below the general average of the earth. We might therefore imagine that during years of powerful solar influence this peculiarity would be increased. Now these observers have found that in this Indo-Malayan region the barometer is abnormally low during times of maximum sun- spots. Again, western Siberia is a district which in the winter season has a pressure decidedly above the average, and we should therefore imagine that during years of powerful solar influence this winter pressure should be peculiarly high. But this is what Blanford has found in his discussion of the Russian stations to correspond with years of maximum sun-spots. 1 Again, Frederick Chambers has enunciated the following laws as resulting from his discussion of various meteorological records: (1) Variations of the sun-spot area are succeeded some months afterwards in the Indo-Malayan region by corresponding abnormal barometric variations, a high barometer corresponding to a mini mum of sun-spots. 2 (2) This lagging behind is greater for easterly than for westerly stations. In other words, this, like other meteorological phenomena, appears to travel from west to east. We may therefore conclude that the barometric evidence as far as it goes is in favour of the hypothesis that the sun is most powerful at times of maximum sun-spots. 105. Rainfall Heights of Rivers and Lakes. In 1872 Mel- drum of the Mauritius Observatory brought forward evidence showing that the rainfalls at Mauritius, Adelaide, and Brisbane were on the whole greater in years of maximum than in years of minimum sun-spots. Shortly afterwards it was shown by Lockyer (Nature, December 12, 1872) that the same law was observable in the rainfalls at the Cape of Good Hope and Madras. Meldrum has since found that the law holds for a great num ber of stations, including eighteen out of twenty-two European observatories, with an average of thirty years observations for each. The results are exhibited in the following table (XXXIV.) : Name of Observatory. Number of Years of Observation. Excess (+) or defcct(-) in maximum Sun-Spot years. 1 St Petersburg 41 31 in 11 11 19 52 53 11 41 39 64 11 41 11 41 39 18 11 41 11 Inches. + 13-08 + 19-65 + 66-85 -22-79 + 10-95 + 0-44 +22-02 + 11-73 +49-90 + 8-90 + 13-84 +23-57 +28-76 + 9-94 -18-35 + 6-44 - 6-16 -11-81 + 18-30 + 5-05 + 4-55 + 10-86 2. Christiania 3 Edinburgh 5. Berlin 6. Utrecht 9. Breslau 10 Bonn 12. Prague 13. Paris 14. Vienna 16. Nicolaieff 17. Geneva 18. Milan 19. Rome 20. Lisbon 21. Palermo 22. Athens It would, however, appear from the observations of Governor Eawson that the rainfall in Barbados forms an exception to this rule, being greatest about the times of minimum sun-spots. 106. Gustav Wex in 1873 3 showed that the recorded depth of water in the rivers Elbe, Rhine, Oder, Danube, and Vistula for the six sun-spot periods from 1800 to 1867 was greater at times of maximum than at times of minimum sun-spot frequency. These conclusions have since been confirmed by Professor Fritz. 4 Quite recently Stewart (Proc. Lit. and Phil. Soc. of Manchester, 188 2) has treated the evidence given by Fritz as regards the Elbe and Seine in the following manner. He divides each sun period, without regard to its exact length, into twelve portions, and puts together the recorded river heights corresponding in time to similar portions of consecutive sun periods. He finds by this means residual differences from the average representing the same law whether we take the whole or either half of all the recorded observations, and whether we take the Elbe or the Seine. The law is that there is a maximum of river height about the time of maximum sun-spots and another subsidiary maximum about the time of minimum sun-spots. There is some reason too to think that the Nile and Thames agree with those rivers in exhibiting a maximum about the time of maximum sun-spots and a subsidiary maximum about the time of minimum sun-spots, only their sub sidiary maximum is greater than it is for the Elbe and Seine. 1 Watvt-f, November 25 and December 2, 1880. 2 A ature, March 18, 1880. 3 Ingenieur Zeitschrift, 1873. 4 I eber die Reziehungen der Sanncnftecken Periode m den Jfagnttischen und .Wettoroloyisfhfti Erscheinungcn der nle, Haarlem, 1878. 107. In 1874 G. M. Dawson came to the conclusion that the levels of the great American lakes were highest about times of maximum sun-spots. In this investigation the value of the evidence derived from rivers and lakes is no doubt greater than that derived from any single rainfall station, inasmuch as in the former case the rainfall of a large district is integrated and irregu larities due to local influence thus greatly avoided. 108. Dr Hunter, director-general of statistics in India, has recently shown (Nineteenth Cent ury, November 1877) that the recorded famines have been most frequent at Madras about the years of minimum sun-spots years likewise associated with a diminished rainfall. 109. Winds and Storms. Meldrum of the Mauritius Obser vatory found in 1872, as the result of about thirty years observa tions, that there are more cyclones in the Indian Ocean during years of maximum than during years of minimum sun-spots. 5 The connexion between the two is exhibited in the following table : TABLE XXXV. Comparison of the Yearly Number of Cyclones occurring in the Indian Ocean with the Yearly Number of Spots on the Sun. Char acter as regards Sun- Spots. Number of Hurri canes. Number of Storms. Number of Whole Gales. Number of Strong Gales. Total Number of Cyclones. Number of Cyclones iu Max. and Miu. Periods. ( 1S47 B

o

r&amp;gt; } Max. 1848 6 2

8&amp;gt; 23 I 1849 3 3 3 2 10 j 1850 4 3 1

8 1851 4 2 1

7 1852 5

3

8 1853 1 1 5 1 8 Min. ] 1854 1855 1856 3 3 1 1 2

2

1 1 13 1857 2 1 1

4 1858 3 1 3 2

Max. 1859 18&amp;lt;iO 3 7 2 4 6 2 4

15) 13}- 3S) ( 1861 5 2 2 2 11) 1862 4 2 2 2 10 1863 5 2 1 1 9 1864 2 2 1

5 MlnJ 1865 1866 1867 2 1

2 4 4 3 2 2

1

11 6} - I 1868 3 3 2

7 Max. J. 1869 1870 1871 3 2 3 1 1 2 3 5 3 2 3 3 9) 11 11) 31 1872 6 5 1 1 13 1873* 4 5 3

1- In 1873 M. Poe y 6 found a similar connexion between the hurri canes of the West Indies and the years of maximum sun-spots. He enumerated three hundred and fifty-seven hurricanes between 1750 and 1873, and stated that out of twelve maxima ten agreed. 110. In 1877 Mr Henry Jeula, of Lloyd s, and Dr Hunter found that the casualties on the registered vessels of the United Kingdom were 17i per cent, greater during the two years about maximum than during the two years about minimum in the solar cycle. 111. Temperature. Baxendell, in a memoir already quoted, was the first to conclude that the distribution of temperature under different winds, like that of barometric pressure, is sensibly in fluenced by the changes which take place in solar activity. In 1870 Piazzi Smyth published the results of an important series of observations made from 1837 to 1869 with thermometers sunk in the rock at the Royal Observatory, Edinburgh. He con cluded from these that a heat wave occurs about every eleven years, its maximum being not far from the minimum of the sun-spot cycle. Sir G. B. Airy has obtained similar results from the Greenwich ob servations. In 1871 E. J. Stone examined the temperature obser vations recorded during thirty years at the Cape of Good Hope, and came to the conclusion that the same cause which leads to an excess of mean annual temperature at the Cape leads equally to a dissipation of sun-spots. Dr W. Kb ppeu in 1873 discussed at great length the connexion between sun-spots and terrestrial temperature, and found that in the tropics the maximum temperature occurs fully a year before the minimum of sun-spots, while in the zones beyond the tropics it occurs two years after the minimum. The regularity and magnitude of the temperature wave are most strongly marked in the tropics. 112. The evidence now given appears at first sight to be antago nistic to that derived from the other elements both of magnetism and meteorology, and to lead us to conclude that the sun heats us most when there are fewest spots on its surface. This conclusion will not, however, be strengthened if we examine the subject with greater minuteness. _ 5 Br. Assoe. Reports, 1872. 6 A. Poe y, Sur les Rapports rntrt tfs Tachts, Solaires et la Ouragans des Antilles, &amp;lt;&. rAtlan tique-Xord, et de I Ocean Indien Sud.
 * Up to May 31.